The present invention generally relates to a semiconductor laser apparatus, and more particularly, to a semiconductor laser apparatus applicable to an optical source for use in an optical recording apparatus such as a facsimile machine, a copier and a printer.
It is known to use a semiconductor laser apparatus as an optical source. A conventional semiconductor laser apparatus includes a semiconductor laser, a collimator lens and a slit plate for shaping a scanning beam emitted from the semiconductor laser. The collimator lens and the slit plate are arranged on an optical axis of the semiconductor laser.
FIGS. 1 through 3 show an example of the conventional semiconductor laser apparatus. Referring to these figures, a semiconductor laser 1 is attached so as to be inserted into an engagement hole 2a formed in a base 2 in a state where the semiconductor laser 1 is pressed by a presser plate 3. A back surface of the presser plate 3 is pressed and held by a laser drive board 4, which is secured on board holders 6 by screws 5. The board holders 6 are secured to a plate by screws (not shown). A plate 7 is secured to the base 2 by two screws 8. On the laser drive board 4, there are mounted an electric circuit used for driving the semiconductor laser 1. Leads extending from the semiconductor laser 1 penetrate the presser plate 3, and are connected to terminals of the electric circuit formed on the laser drive board 4 by soldering. A lens holder 10 which accommodates a collimator lens 9 is secured to the plate 7. A wave-shaped washer 11 for eliminating the occurrence of back rush is interposed between the lens holder 10 and the plate 7.
The front of the plate 7 is covered with an aperture holder 12, which is secured to the plate 7 by a screw 13. The aperture holder 12 has a cylindrical portion 12A, at an outlet end of which there are formed two craws 12A-1 and 12A-2 opposite to each other. A cutout 12A-3 is formed in an edge portion of the cylindrical portion 12A. In the cylindrical portion 12A, there is formed a step portion 12A-4.
A slit plate 14 has a slit 14A for shaping the laser beam emitted from the semiconductor laser 1, engagement edges 14B-1, 14B-2 and 14B-3 which fit an inner wall of the cylindrical portion 12A, and a projection portion 14C which engages with the cutout 12A-3. The slit plate 14 is slightly wider than the distance between the opposite ends of the craws 12A-1 and 12A-2. The slit plate 14 is positioned in the cylindrical portion 12A as follows. The first step is to make the projection portion 14C engage with the cutout 12A-3. The second step is to pass the slit plate 14 over the craws 12A-1 and 12A-2 by utilizing elasticity thereof. The third step is to fit the engagement edges 14B-1, 14B-2 and 14B-3 to the inner wall of the cylindrical portion 12A.
In the above-mentioned semiconductor laser apparatus, the collimator lens 9 is used for collimating the divergent laser beam emitted from the semiconductor laser 1. Conventionally, two adjustments are needed for suitably collimating the laser beam. One of the adjustments is an optical axis adjustment which aims to have the optical axis of the collimator lens 9 coincide with the optical axis of the semiconductor laser 1. The other adjustment is to have a light emission point of the semiconductor laser 1 coincide with the focal position of the collimator lens 9.
However, a long time is taken to perform the above-mentioned adjustments. This prevents the reduction in costs for manufacturing semiconductor laser apparatuses. For example, referring to FIG. 3, the optical axis adjustment is carried out by relatively shifting the base 2 onto which the semiconductor laser 1 is fastened, and the plate 7 on which the lens folder 10 is mounted. Thereafter, the base plate 2 and the plate 7 are mutually secured by the two screws 8. The above-mentioned adjustment is very troublesome.